Survey of fish assemblages in the upper Neversink River and upper Rondout Creek, New York, 2017–19

Streams in the Catskill Mountains region of New York provide many important ecological and economic services, including recreational angling and serving as a drinking water supply to New York City. Many streams in this region were adversely affected by acid deposition during the late 20th century, impairing water quality and aquatic ecosystems. More recently, the level of acid deposition has declined while changes in climate have become more pronounced. As a result, biological and chemical data are needed to determine the current condition of stream ecosystems in the Catskill Mountains region. The U.S. Geological Survey, in cooperation with the Rondout Neversink Stream Program, surveyed fish communities and water chemistry annually between 2017 and 2019 at 23 sites in the upper Neversink River and upper Rondout Creek watersheds to compile a contemporary baseline dataset and assess potential biological recovery from reduced acidification. The resulting data indicated that brook trout (Salvelinus fontinalis) were present at every study site, although slimy sculpin (Cottus cognatus) was the most abundant species at most sites. Stream pH ranged from 4.8 to 7.0 across all sites and generally increased from upstream to downstream. Similarly, the number of species present and the ratio of brown trout (Salmo trutta) to brook trout increased at sites in each subwatershed from upstream to downstream. Introduction The Neversink River and Rondout Creek are historic trout fishing and recreational streams in the heart of the Catskill Mountains of southeastern New York. Both streams played an important role in the origins of fly fishing in the United States, and continue to be used heavily by anglers (Van Put, 2007). During the second half of the 20th century, however, the headwaters, tributaries, and some main stem reaches of both rivers were adversely affected by acid deposition. Surveys during the late 1980s and early 1990s found that some or all fish species were absent or their populations were depressed in many reaches of both river systems because of elevated acidity and concentrations of inorganic monomeric aluminum compounds (Baker and others, 1996; Baldigo and Lawrence, 2000, 2001). More recently, acid deposition and stream acidity have declined in the Catskill Mountains region (McHale and others, 2017), and climate change is an increasing threat that is affecting stream flow and temperature regimes across the northeastern United States (DupignyGiroux and others, 2018). Quantitative information on fish assemblages in the Catskill Mountains region is needed to assess the current health of stream ecosystems, evaluate potential biological recovery from decreasing acidification, and document the effects of climate change, invasive species, and other stressors on important natural resources. In 2017, the U.S. Geological Survey (USGS) and the Rondout Neversink Stream Program initiated a study to determine the current status of fish assemblages and water chemistry across the watersheds of the upper Neversink River and upper Rondout Creek. The objectives of this study were to obtain a contemporary dataset that could be used to evaluate recovery from acid deposition and serve as a baseline for evaluating future changes in the watershed from climate change, invasive species, and other stressors. The information obtained in this study may be used to inform and assess future management actions in these watersheds related to stream restoration, trout stocking, and angling regulations. Equipment and Methods Fish communities were surveyed annually from 2017 to 2019 at study sites within the upper Neversink River and upper Rondout Creek watersheds (fig. 1). The study area was limited to the reaches upstream from the Neversink and Rondout reservoirs. A total of 23 study sites were surveyed annually for 3 years (table 1), with the exception of the DTHall site on the East Branch Neversink River, which was not sampled in 2017, and the WBGage site on the West Branch Neversink River, which was not sampled in 2018. The sites ranged in drainage area from 0.3 to 172.5 square kilometers. Fish assemblages were surveyed between late June and early August using multipass depletion electrofishing surveys. During each survey, fish were collected from seine-blocked reaches in three or four consecutive passes with one person 2 Survey of Fish Assemblages in the Upper Neversink River and Upper Rondout Creek, New York, 2017–19 We st B ran ch Ne ver sin k R ive r East B ran ch Ne ver sin k Ri ver Ro nd ou t C ree k Deer Oasis AbvBHB WBGage EBGage Tisons EMtRoad Sundown EVRanch Biscuit DSPeekLk USPeekLk BlueHill Ballfield CovBridge Winnisook